Dual-homing probing improvements

(1) Active probing mechanism in the following two scenarios
    (1-1) Probe all ports on the pair device within the same vlan (excluding the pair port) when the 1st location of a host is learnt
    (1-2) Probe again when a device/port goes down and comes up again
    * Introduce HostLocationProvingService
        - DISCOVER mode: discover potential new locations
        - VERIFY mode: verify old locations
    * Can be enabled/disabled via component config
    * Improve HostHandlerTest to test the probing behavior

(2) Fix an issue that redirection flow doesn't get installed after device re-connects

(3) Temporarily fix a race condition in HostHandler by adding a little bit delay

Change-Id: I33d3fe94a6ca491a88b8e06f65bef11447ead0bf
diff --git a/apps/segmentrouting/src/test/java/org/onosproject/segmentrouting/MockLocationProbingService.java b/apps/segmentrouting/src/test/java/org/onosproject/segmentrouting/MockLocationProbingService.java
new file mode 100644
index 0000000..b0cdf43
--- /dev/null
+++ b/apps/segmentrouting/src/test/java/org/onosproject/segmentrouting/MockLocationProbingService.java
@@ -0,0 +1,74 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.segmentrouting;
+
+import com.google.common.collect.Lists;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Host;
+import org.onosproject.net.host.HostLocationProbingService;
+
+import java.util.List;
+import java.util.Objects;
+
+public class MockLocationProbingService implements HostLocationProbingService {
+    List<Probe> probes;
+
+    private class Probe {
+        private Host host;
+        private ConnectPoint connectPoint;
+        private ProbeMode probeMode;
+
+        Probe(Host host, ConnectPoint connectPoint, ProbeMode probeMode) {
+            this.host = host;
+            this.connectPoint = connectPoint;
+            this.probeMode = probeMode;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) {
+                return true;
+            }
+            if (!(o instanceof Probe)) {
+                return false;
+            }
+            Probe that = (Probe) o;
+            return (Objects.equals(this.host, that.host) &&
+                    Objects.equals(this.connectPoint, that.connectPoint) &&
+                    Objects.equals(this.probeMode, that.probeMode));
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(host, connectPoint, probeMode);
+        }
+    }
+
+    MockLocationProbingService() {
+        probes = Lists.newArrayList();
+    }
+
+    boolean verifyProbe(Host host, ConnectPoint connectPoint, ProbeMode probeMode) {
+        Probe probe = new Probe(host, connectPoint, probeMode);
+        return probes.contains(probe);
+    }
+
+    @Override
+    public void probeHostLocation(Host host, ConnectPoint connectPoint, ProbeMode probeMode) {
+        probes.add(new Probe(host, connectPoint, probeMode));
+    }
+}